1. Field of the Invention
This invention relates to a curtain air bag for vehicles, adapted to protect crew against a shock occurring when a vehicle is collided.
2. Description of the Related Art
The related art air bags adapted to protect crew (seat occupants) against a shock occurring when collided in the longitudinal direction, and an air bag adapted to protect crew against a shock occurring when collides, and against an impact occurring when the vehicle rolled over.
Out of these air bags, the air bag adapted to protect a passenger against an impact occurring when collided (side collision) with a side of a vehicle, or against an impact occurring when the vehicle is rolled over is stored in a folded state in side portions of a roof of the vehicle. When a vehicle is collided or is rolled over, a high-pressure gas is ejected from an inflator, by which gas the air bag is deployed in a curtain-like shape along an inner side surfaces of the interior of the vehicle. For this reason, this type of air bag is called a curtain air bag.
There is a known curtain air bag of this kind (see Japanese Patent Laid-open Publication No. JP-A-2004-34766 and corresponding U.S. patent application Publication US 2004/0056456 A1), in which a main inflatable chamber is formed by mutually communicating a front protective area and a rear protective area with each other. An auxiliary or minor inflatable chamber is formed in a portion of the air bag which is arranged between the front protective area and the rear protective area. The front protective area is communicated with the auxiliary inflatable chamber via a vent hole 31. Therefore, when the inner pressure of the main inflatable chamber increases due to a load by which the deployed air bag restrains the crew, a part of the gas in the main inflatable chamber formed by the front and rear protective areas is made to flow into the auxiliary inflatable chamber via the vent hole to thereby cause the pressure in the main inflatable chamber to decrease. As a result, the occurrence of a rebounding phenomenon is avoided by reducing a peak acceleration which the crew receives.
However, in the above-described related art curtain air bag, a partition wall defining the main inflatable chamber and auxiliary inflatable chamber as well as the partition wall defining the front protective area and the rear protective area in the main inflatable chamber are formed by sewing an air bag body by two sewing lines separated from each other. Therefore, the partition walls are necessarily formed so as to have a predetermined substantial width.
As a result, in the related art curtain air bag, a substantial protective area with respect to the crew decreases due to the existence of the partition wall between the main inflatable chamber and the auxiliary inflatable chamber as well as the partition wall defining the front protective area and the rear protective area.